This invention relates generally to operator interface systems for controlling the movement and operation of a work machine and, more particularly, to a differential pedal interface system for controlling the locomotion of a work machine.
Currently, when driving a work machine such as a wheel loader, the machine operator is faced with simultaneously controlling machine speed, jerk, acceleration, deceleration, direction, steering and implements. In fact, control of some of these parameters is achieved indirectly. For example, when driving a conventional wheel loader, the operator controls the operation and performance of the machine through a conventional interface system which includes operating and controlling a plurality of interface devices such as a throttle pedal, impeller clutch/brake pedal, brake pedals, toggle and other types of switches, steering wheel or joystick, implement levers or joystick, and other interface controls. Typically, a combination of operator control inputs to a plurality of the above-identified control inputs are necessary in order to achieve a specific control function such as speed, acceleration, deceleration, forward or reverse movement, steering and implements. Conventional interface speed control functions in the forward or reverse direction likewise involve use of both feet, while low speed operation is further complicated by machine-to-machine variations associated with the impeller-brake pedal adjustment. In order to achieve desired speed on certain wheel loaders, the operator controls engine torque by varying the throttle setting. In order to maneuver the machine at slow speeds, the operator must control both the throttle setting and the impeller clutch pedal. Also, acceleration of the machine involves control inputs different from the inputs necessary to achieve deceleration of the machine. In addition, often times switches such as a forward/reverse direction switch needs to be actuated and coordinated with movements of the operator""s feet while steering and otherwise controlling the machine. To effectively control all of these parameters, while simultaneously manipulating the plurality of interface devices, requires that the operator have extensive experience in operating and controlling the particular machine.
In this regard, it would be beneficial to control machine parameters in a direct fashion so as to reduce the total number of control inputs which must be exercised by the operator. This can be accomplished by consolidating intuitively associated variables with a particular input. However, this puts a greater emphasis on the operator""s ability to precisely control the particular input. Therefore, while it is possible for an inexperienced operator to adequately control a particular machine, the operator will normally not be able to take advantage of the machine""s full potential or capability until after some operator time has been achieved. It is therefore desirable to have an operator interface system which is simple, intuitive, predictable, precise and easy to learn.
Additionally, terrain irregularities have the potential to be transferred into undesirable control inputs. Uneven terrain and other irregularities are common in the work environment where these types of machines are routinely used and, often times, such uneven terrain affect the various operator inputs to control the operation of the machine. As a result, it is often necessary for the operator to operate the machine at a substantially lower speed when encountering irregular terrain. Operating the machine at lower speeds reduces the ability to complete a particular task.
Irregular terrain therefore translates into unwanted mechanical disturbances which may be inputted to the machine via the operator input system. Consider, for example, a single pedal whose position is mapped into desired machine speed. As the operator varies the pedal""s displacement, the machine accelerates or decelerates to match the speed setting marked by the pedal""s position. The operator""s ability to precisely control such input may be satisfactory on a smooth highway, but will degrade substantially when the machine travels over rough terrain or engages in a cycling application such as truck loading. In fact, when the machine travels over bumps, the operator""s foot will bounce, resulting in abrupt changes in the requested speed, causing sudden acceleration and deceleration of the machine, or jerk, with the potential for self-excitation to occur in the operator-machine interface system.
Since conventional interface systems are complicated and cumbersome to control, particularly for an inexperienced operator, it is desirable to design an operator-machine interface system which not only allows inexperienced operators to easily utilize the machine""s full potential, but which allows the speed, acceleration, deceleration and jerk of the machine to be controlled through a minimum number of operator inputs. It is also desirable to provide an interface system which will effectively cancel unwanted mechanical disturbances due to travel over irregular terrain.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, an operator-machine differential pedal interface system is disclosed wherein a pedal arrangement is positioned and located in the operator compartment, the present pedal system being symmetrically located to the left and right of the steering column such that the operator can comfortably deflect such pedals with the left and right foot respectively. The present pedals are linked in such a way that if one pedal is deflected in a certain direction, the other pedal moves an equal amount in the opposite direction. Also, one pedal controls movement in the forward direction and the other pedal controls movement in the reverse direction. For example, the right pedal can be configured to control movement in the forward direction whereas the left pedal can be configured to control movement in the reverse direction. In the absence of control input from an operator, the present pedal system includes a mechanism for self-centering the respect pedals to a neutral position.
Importantly, several embodiments of the present pedal system include at least one sensor positioned and located so as to output a signal indicative of the relative position or displacement of the pedals in either the fore or aft direction relative to a centered/neutral position. This position sensor is coupled to an electronic control module (ECM), or other processing or controller means, and continuously outputs signal(s) to the ECM indicative of pedal displacement. Based upon both pedal position and the rate of movement of such pedals, the ECM, or other control means, is programmed to output appropriate signals to appropriate machine control systems to control the speed, acceleration, deceleration, and jerk of the machine in either the forward or reverse directions. For example, if the right pedal is configured to control forward movement of the machine and the left pedal is configured to control reverse movement of the machine, movement of the right pedal in a forward direction away from a centered or neutral position will be interpreted by the ECM as an operator input command requesting that the machine accelerate to and achieve a desired machine speed in the forward direction. The acceleration of the machine to the desired speed is a function of the rate of movement and/or position of the right pedal in the forward direction, and the requested final speed of the machine is a function of the final position or displacement of the right pedal relative to the centered or neutral pedal position. The rate of movement of the right pedal can be determined by the ECM based upon the relative change of the displacement of the pedal over time. The same correlation is likewise true with respect to movement of the machine in the reverse direction, the acceleration and final speed of the machine in the reverse direction being controlled by the final position and rate of movement of the left pedal in a forward direction relative to the centered or neutral pedal position. Deceleration of the machine is likewise a function of the rate of movement and/or position of the pedals.
Jerk of the machine is likewise controlled through the maps programmed into the ECM. In addition, since the present pedal system is coupled together such that the respective pedals move in an equal and opposite direction relative to their respective centered or neutral positions, unwanted mechanical disturbances due to travel over irregular terrain as well as other unwanted operator inputs can be more easily controlled since both feet of the operator rests on the pedals and one foot functions to stabilize and control inputs from the other foot, whether these inputs are wanted or unwanted. Use of both feet in conjunction with the differential movement of the present pedal system therefore enables an operator to brace and prevent unwanted pedal displacement due to machine jerk which may result from terrain irregularities, aggressive machine operation, or other sources.
The present pedal system may also include a self-centering mechanism, and a speed control mechanism for further controlling the movement and operation of a particular work machine. In this regard, the self-centering mechanism ensures that the differential pedal system returns to its centered or neutral position whenever the operator is not inputting control to the pedals; and the speed control mechanism enables the operator to select a maximum speed for the machine based upon certain environmental or operating conditions.
In another aspect of the present invention, the present differential pedal system is operatively connected directly to the hydrostatic transmission or other transmission system associated with a particular work machine such that differential movement of the foot pedals will selectively engage the transmission such that the work machine is operated in either the forward or the reverse direction. In this particular embodiment, no ECM is utilized and the speed, direction, acceleration, deceleration and jerk of the work machine will be proportional to the position and rate of change of the swash plate and the swash plate angle respectively of the transmission, which swash plate position and angle will likewise be proportional to the displacement and rate of change of the differential pedals.
The various embodiments of the present differential pedal system therefore function as a single operator control input to control the speed, acceleration, deceleration and jerk of a particular work machine in both the forward and reverse directions. The present systems lead to a high degree of precision with respect to controlling desired machine speed, acceleration, deceleration, jerk, and machine direction; they provide better control of the machine over rough terrain thereby allowing the operator to operate the machine at higher speeds resulting in higher productivity; and they allow inexperienced operators to easily and controllably utilize the machine to its fullest potential. In addition, the present systems represent simple, intuitive, predictable and easy to learn interface systems which greatly enhances machine utilization under a wide variety of different operating conditions and such systems can be easily coupled and operatively connected to appropriate machine systems such as engine and transmission control systems for selectively controlling the locomotion of the machine.
The present differential pedal systems can be incorporated into any type of work machine in accordance with the teachings of the present invention.